Unconditionally free and zero in binaryBlob::clear()

The function previously conditionally freed a m_memblocks pointer if its
corresponding m_headers was valid. This makes me slightly worried about
the possibility that memory would be allocated, but the header would
still be marked as invalid.

I don't see how that could happen, but it's better to be safe than
sorry. SDL_free() does a guaranteed NULL pointer check (like most SDL
functions), so it's okay to pass NULL pointers to it.

Just to be sure, I'm also zeroing m_memblocks and m_headers after
freeing everything in the function.

desktop_version/src/BinaryBlob.cpp

@@ -139,12 +139,10 @@ void binaryBlob::clear()
 {
 	for (size_t i = 0; i < SDL_arraysize(m_headers); i += 1)
 	{
-		if (m_headers[i].valid)
-		{
-			SDL_free(m_memblocks[i]);
-			m_headers[i].valid = false;
-		}
+		SDL_free(m_memblocks[i]);
 	}
+	SDL_zeroa(m_memblocks);
+	SDL_zeroa(m_headers);
 }
 
 int binaryBlob::getIndex(const char* _name)